The Martian Chronicles

M'gann's White Martian mate Armek comes to Earth to bring her back to face justice for her "treachery' When she takes refuge in the DEO, Armek infiltrates the building and uses his shapeshifting powers to spread confusion.

Recap

Kara arrives at the bar and sees Mon-El behind the bar. He gets her a
club soda and she tries to talk about their conversation. Kara tells
him that it's nice that he was honest, but he was right: she's not sure
that they're a good match. She tells Mon-El that it's the way he is, and
Mon-El excuses himself. Alex comes over and Kara tells her about her
problems, and then suggests that for her 13th anniversary since she
landed on Earth, they go line-dancing. Alex tells her foster sister that…